The fire-break wall between the transformers, and the exterior wall of the turbine hall, must be compliant with F30, F60 fire protection ratings (30 or 60 minute fire resistance—fire-retardant or highly fire-retardant) and, in some instances, with more stringent requirements. In general, this poses no problems for the execution of the wall, in structural terms. However, the requisite openings for a generator busduct, of height ranging from 800 mm to 1440 mm and of width in excess of 4000 mm, are such that the stipulated fire protection requirements cannot be observed. This is due to the fact that, at a temperature of ≧500° C. in the event of a fire, a generator busduct of aluminum construction which is built-in or embedded in the opening will melt, thereby producing openings in the wall (corresponding to the diameter of the 3-phase-isolated generator busduct enclosure), thus permitting the fire to penetrate from one side of the wall to the other.
In a known form of construction for the protection of the area surrounding the outer shell, it is provided that the opening on either side of the fire-break wall is closed by a double-sided sheet aluminum cladding, whereby a mineral wool filling is also provided between the two metal plates. In place of mineral wool, “fire-break panels” of approximate thickness 20 mm (combined in plurality in a sandwich construction) are also used. However, even in this form of construction, the openings are not completely closed, such that fire protection requirements are not observed.